Determination of Selenium in Food Samples by High-Resolution Continuum Source Atomic Absorption Spectrometry After Preconcentration on Halloysite Nanotubes Using Ultrasound-Assisted Dispersive Micro Solid-Phase Extraction

In this study, a preconcentration procedure was developed for the determination of selenium in food samples using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS). Halloysite nanotubes (HNTs) were used as a solid sorbent in ultrasound-assisted dispersive micro solid-phase extraction (USA DMSPE) during the preconcentration step. The experimental parameters including pH of the sample solution, the amount of halloysite nanotubes, and ultrasonication time, as well as the main parameters of HR-CS GFAAS, were optimized. The limit of detection of total selenium was 0.01g/L and the achieved preconcentration factor was 18. The relative standard deviations (RSDs) were 6-9%. The accuracy of this method was validated by analyses of NIST SRM 1567a (wheat flour) and NIST SRM 1549 (non-fat milk powder) certified reference materials. Selenium contents measured in these reference materials were in satisfactory agreement with the certified values according to the t test for a 95% confidence level. The proposed method was successfully applied to the determination of selenium in food samples (corn flour, rice flour, oat flour, buckwheat flour, garlic, cranberries, goji berries, and raisins).